Ad libitum feeding from hoppers offers a simple system for feeding growing pigs and maximises liveweight gain. High feed intake in the later stages of production often results in excessive backfat deposition, making it difficult to achieve optimum carcass gradings with pigs kept to bacon weight. Both nutrient density of the diet and ambient temperature may influence voluntary feed intake. This experiment investigated the extent to which these factors could be used under commercial conditions to manipulate growth rate and fat deposition of pigs on an ad libitum feeding system.